Optoelectronic components or active optical devices such as diode lasers, light-emitting diodes (LEDs), and photodiode detectors are used for printing, data storage, optical data transmission and reception, laser pumps, and a multitude of other applications. Most optoelectronic components are typically sealed inside a hermetically sealed package for performance requirements and operational stability. Optoelectronic packages are intended to provide a hermetic structure to protect passive and active optical elements and devices as well as related electrical components from damage resulting from moisture, dirt, heat, radiation, and/or other sources.
For high-speed applications (e.g., 2 Gbps and above), proper operation of the optical and/or electrical components inside the package may be affected unless careful attention is paid to the packaging of these components. Standard optical module packaging such as that used in optical telecommunication applications requires a hermetic enclosure. Sealed packages are necessary to contain, protect, and electrically connect optoelectronic components. These requirements have resulted in packages that are large, costly, and more difficult to manufacture than typical electronic packages. In fact, the cost of most optoelectronic devices is mainly dominated by the package rather than the optical devices themselves.
Current designs of optoelectronic packages and associated fabrication processes are not easily adapted for automated manufacturing techniques because conventional packages for optoelectronic components such as large so-called “butterfly” packages are characterized by numerous mechanical parts (submounts, brackets, ferrules, etc.), and three-dimensional (3D) alignment requirements. Butterfly packages are basically can-and-cover type arrangements that contain an optical subassembly mounted to a metallic baseplate, with leads coming out of the sides for electrical connections. The optical subassembly may be built up separately, outside of the can, and then later installed in the can. The circuits within the optical subassembly are wire-bonded to the leads of the butterfly can, which is then sealed with a lid to create a hermetic enclosure. Unfortunately, conventional butterfly cans are bulky, costly, and time-consuming to manufacture. In addition, the electrical components require a separate electrical subassembly that is located outside of the butterfly can. The requirement of a separate electrical subassembly that is separate and apart from the optical subassembly inside the butterfly can increases manufacturing costs significantly.
Transistor-Outline (TO) packages are also commonly used to house optoelectronic components. Conventional TO packages include a generally cylindrical metal cap and a metal header or base, to which the metal cap is attached. In such packages, metal-based bonding techniques such as, for example, brazing or fusion welding, are often required to provide a hermetic seal between the metal cap and the header. To weld the metal cap onto the header, the header is typically formed of a metallic material such as Kovar™ or stainless steel. However, it is advantageous to use ceramic bases in connection with high-speed applications because ceramic bases are ideal for RF applications. Particularly, ceramic headers provide easy routing of high-speed circuits. Unfortunately, ceramic is not compatible with metal with regard to weldability, and therefore has not been widely used as the material for the header or base in conventional TO packages.
In addition, when active optical devices (e.g., diode lasers) and integrated circuits adapted to control the active optical devices (e.g., diode drivers) are spaced too far apart from each other, parasitic capacitance, resistance, and/or inductance may affect electrical signals traveling between the components, thus resulting in degradation of the electrical signal. The electrical performance is of particular concern for high-speed applications. Consequently, electrical performance may be improved during high-speed applications when the distance between the active optical device and its associated driving or receiving integrated circuit chip is as short as possible. Although this arrangement improves the electrical signal integrity, it increases heat dissipation requirements of the assembly significantly.
As the power density increases in optoelectronic devices and/or electrical components used in high-speed applications, a suitable, optimal heat sink is necessary to dissipate heat efficiently from the optoelectronic device and/or electrical components. Heat sinks are devices capable of dissipating heat away from the optoelectronic and/or electrical components into the surrounding atmosphere by convection. Typical heat sinks include cooling fins attached to a heat sink base that is in contact with the header or base of the optoelectronic package. The fins of the heat sink may have any shape and size necessary to spread heat away from the optoelectronic device and/or electrical components, and may be oriented either parallel or perpendicular relative to the base of the optoelectronic package.
Commercially available heat sinks are generally square or rectangular in shape. As such, the circular headers of conventional optoelectronic packages require either modifications to the structural design of the heat sinks to be able to accommodate the circular headers, or manufacturing adjustments to attach the circular header to the square or rectangular heat sink. This configuration results in a complex, slow, and expensive manufacturing process. Additionally, the quality of the contact between the optoelectronic package and the attached heat sink has a great impact on the overall thermal performance. Lower thermal impedance between the optoelectronic package and the heat sink results in higher conductive heat transfer. Therefore, it is advantageous that the header of the optoelectronic package be in intimate, conformal contact with the attached heat sink to optimize the thermal characteristics, which results in increased efficiency.
Moreover, existing optoelectronic packaging techniques often involve manual or semi-automated manufacturing processes. Therefore, to reduce manufacturing costs, it is advantageous to employ automated batch packaging processes that can fabricate a large number of optoelectronic packages simultaneously.
Therefore, there is a need for an improved optoelectronic package and a process for making the optoelectronic package that can address some or all of the problems described above.